As a proud grad of "OP Amps 101, Real World Addition" from KISS University, I thought I was now qualified to do OpAmpy stuff with a genaral understanding of the basics.
Wrong. I need "OP Amps 102".
I SIMed the below TL081 virtual ground Split Rail power supply circuit from a similar 1/2 TL082 circuit in the most recent issue of the ARRL's QST April 2014 magazine (page 41) by David L. Chute, KG4BZW. It is used in a very nice, 2 chip TL082 home brew ESR meter:
I built this circuit this morning using 1/2 of a TL082 and the real thing confirms the SIM, except that the rail values are slightly (20mV or so) lower.
No load circuit draws about 18mA. Rail loads of 20mA or so reduce rail voltage levels 15% to 20%.
I am assuming there is some cap charging going on, but I have seen some similar circuits from google searches without the caps. Didn't build one of those.
My questions are:
1. how does this particular circuit work? (Simple answers, please, suitable for a Level 102 student...)
2. can the load carrying capacity of the circuit be increased?
(Wish I'd known about this before my radiator fan fault monitoring post(s) where I bought some MAX1044s).